DVB-T(sd) is more robust(easier to recieve over longer distances) than HDDVB-T. The difference between the 2 is :
DVB-T only recieves standard definition signals(about 780p resolution)
DVB-T (HD) recieves high definition signals (1080p resolution) but is harder to recieve than SD.
You will find that the dvd player with the DVB-T (HD) should do both signals (SD and HD)check the specs.
ISDB-T is not available in Australia.